This invention relates to a process for manufacturing large-length and large-diameter hoses.
In the present specification the term "large-diameter hoses" refers to hoses having a diameter ranging from 50 mm to 1000 mm, and the term "large-length hoses" applies to those being longer than 50 m.
It is known, that the raw materials of the elastomer layers of large-diameter, large-length hoses may be any flexible materials; the materials may be both thermoplastic or also thermosetting ones. The most valuable hose-manufacturing processes are those enabling the application of both thermoplastic and thermosetting materials. Of limited value are processes enabling only the application of materials of one definite type.
Hose manufacturing processes which are known, are suitable for producing large-diameter hoses at lengths ranging up to 50 m. Likewise processes are known by which hoses of no more than 50 mm diameter can be produced in lengths of 50-200 m.
No process is however known by which hoses of 50-1000 mm diameter with lengths over 50 m can be made of any elastomer or plastomer or more than one type.
Various methods have been developed for manufacturing large-length hoses having at least 50 mm diameter. Building a hose usually starts with a tube extruded on flexible mandrel let off drums rotating around a horizontal axis; on this mandrel are applied the reinforcing plies with twisting or braiding from around the longitudinal axis rotating machine having discs. Subsequently after having applied the cover, during cure in a lead-press, the built-up hoses are provided with a pressure-securing casing. The semifinished product thus obtained is wound on a drum rotating around a horizontal axle and subsequently, the hose is wrapped with a lead-sheath and is cured in a large-diameter steam boiler. After cure the flexible mandrel is removed by using hot water; while the lead-sheath is removed by conventional appropriate equipment.
The above process can not be used for the manufacture of large diameter hoses, because with larger diameter flexible mandrels the bending radius increases and due to this, drums of unworkable dimensions would be needed. An additional problem arises in that no machines suitable for extruding tubes or covers for the large-diameter hoses are available. Several hundred, perhaps thousand yarns would have to be simultaneously applied, the known braiding or twisting machines suitable for applying such yarns have, however, no more than 64 spools. There exists, as a practical matter no equipment for applying simultaneously several hundred yarns.
There are several patents disclosing methods for producing large-diameter hoses up to 50 m long. Representative are U.S. Pat. No. 3,037,343 and Hungarian Pat. No. 154,707.
According to the processes disclosed in these patents the reinforcing plies are applied from braked let off stands onto the mandrel rotated and moved lengthwise by a suitable device. The production of larger length hoses is not possible in this way, because for that purpose, production workshops of several hundred meters length need to be available, and suitable, special apparatus would be necessary for supporting the hoses of large-length during manufacture.
An exception is, to a certain extent, the method disclosed in U.S. Pat. No. 4,019,539 with regard to the above disadvantages. This process, however, is also limited in that it can only be used for the production of thermoplastic, and thus, of plastic hoses that require no curing. The process can be used for the production of hoses that are several hundred meters long having, a diameter no more than 400 mm at the best. Such a dimension range also requires use of extraordinary large and expensive apparatus. For example the diameter of the drums used when building such a hose is 10 m. Moving drums of this size can only be performed by using very expensive equipment. Hoses manufactured by using the process disclosed in the patent can only be stored and transported on drums of similar size to that of the manufacturing drums. Therefore, such a plant can only be set up on a seaside and the hoses can only be sold to customers having a seaport or dock who intend to use said hoses in the port or on floating equipment. This is so because drums having a diameter of about 10 m can not be transported on highways or on railways.
The known processes can be used with thermoplastics, for example in the case of applying a Rilsan type polyamide as a plastomer only, while hoses made of materials requiring vulcanization can not be fabricated by using this process.
Another known process the production of large-diameter hoses having a length of 50 m, uses a large size turn-bench with building-up. Building of the individual structural elements onto the rotating mandrel is carried out by means of a servizer moving along the machine.
Recently, customers increasingly require large-length, large-diameter hoses made of rubber or of a combination of rubber and plastics. However, there is no satisfactory process for manufacturing such hoses. An object of the present invention is to provide a process for producing large-diameter, large-length hoses which cannot be manufactured by using prior art techniques.